1. Field of the Invention
The invention relates to a yarn package provided on a yarn package holder such as a tube, a method for winding a yarn on a tube forming a yarn package and to the yarn package forming apparatus.
2. Description of the Related Art
The intended use of a yarn usually determines the packaging method employed. Package holders consist essentially of for example wood, cardboard, or plastic cores on which yarns are wound, and normally have holes in their centers allowing them to fit on spindles or other holding devices. Several forms and dimensions are available. Spools are cylindrical, with end flanges. Cones, having a conical-shaped core, produce a package of conical shape; tubes, with cylindrical-shaped cores, produce cylindrical packages. Cheeses are cylindrical yarn packages wound on a tube, and, unlike most other packages, they have greater diameter than height. Skeins are coils of yarn wound with no supporting core. Yarn packages are often placed in an unwinding machine such as a creel in an approximately horizontal position.
Yarn is a strand composed of fibers, filaments (individual fibers of extreme length), or other materials, either natural or man-made, suitable for use in the construction of fabrics, such as woven, knitted or tufted types.
In one application the strand may consist of a number of fibers twist plied together; a number of filaments twist plied together; a single twist plied filament, called a mono-filament; or one or more twist plied strips made by dividing a sheet of materials, such as paper or metal foil. The properties of the yarn employed greatly influence the appearance, texture, and performance of the completed fabric.
A process and apparatus for making uniform alternate ply-twisted yarn is known from WO 95/25190. This publication describes a process and apparatus for making alternate S and Z twist plied yarn from individual singles yarns including the steps of tensioning the singles yarns as they move in a path through the process, twisting the individual yarns in either an S or Z direction, snubbing the yarn to restrain ply twisting so the twist in the singles yarn can equalize itself, stopping the forward movement of the yarn, then bonding the ply-twisted yarns at a node while applying twist, stopping the twisting operation, then repeating the procedure while twisting in the opposite direction.
Alternate twist plied yarn where the singles strands are twisted in the same direction and are brought together and allowed to spontaneously ply together until the singles twist torque is balanced by the ply twist torque. The single strands are bonded together in the region where the singles twist reverses and they may be bonded in the plied yarn before the singles twist is reversed.
U.S. Pat. No. 4,873,821 describes a process where the alternate ply twisted yarns are bonded in the ply twisted condition before the singles twist is reversed.
Both publications give an example of a twist plied yarn and are hereby incorporated by reference.
More specifically, the twisting action is accomplished by alternate twisting, where for a certain yarn length the yarn is twist plied a number of turns in one direction and then for another sequential length, it is twist plied in the opposite direction. The nature of alternate twisting is such that the total number of turns in one direction minus the total number of turns in the opposite direction over the total yarn-length is zero. The method of taking several twist plied yarns and combining them by twisting them together to make a multi-stranded yarn has been known for years.
Typically, an alternate twist plied yarn shows so called nodes, also denoted as tack zones. These are located in between the S-twist and Z-twist zones or in between the Z-twist and S-twist zones. Nodes or tack zones have substantially zero twist plied; in case of tack zones, the fibers or filaments are e.g. intermingled with each other.
Stable alternate twist plied yarns are known in the art: if one applies tension to the alternate twist plied yarn, this yarn will tend to untwist over the nodes; but when tension decreases, the stable alternate twist plied yarn will twist back to approximately its original twist plied level.
A problem occurring in the prior art with alternate twist plied yarn packages is the fact that these known yarns tend to cause interruptions in the unwinding process, whenever the yarn is rolled off the bobbin for further processing. It has been noticed that they tend to burst or break upon unwinding, or at least show tension peaks in the unwound yarn. This unwanted movement of the yarn is caused by a tension residue within the yarn winded on the bobbin. A release of the yarn will cause a decrease in the tension and provoke a rolling movement of the alternate twist plied yarn. This unwanted behavior may cause interruption and even product failure upon winding.
The invention provides a yarn package wherein this problem is solved.
During winding this yarn on the winder, the yarn winding tension results in an untwisting or detwisting of the yarn on both sides of the nodes. During unwinding, which may occur at low speed, the yarn tension in the yarn decreases. This tension decrease results in a self-twisting rotation of the yarn. When the tension of an alternate twist plied yarn decreases a S-Z node will rotate clockwise for at least several rotations, the reverse will happen at a Z-S node i.e. counter clockwise rotation for several rotations. The intensity of the rotations depends on several different aspects, such as the nature and thickness of the yarn, the twist plied level, etc.
Due to this self-twisting rotational movement of the yarn it might be possible that the yarn rolls to the back off the bobbin and even falls over the edge of the yarn package in the opposite direction of the unwinding direction such that further unwinding becomes impossible. In an unwinding apparatus the yarn tension will become destructive for the yarn, which will ultimately burst. These unwanted situations cause damage not only to the yarn, but harm the total unwinding process, resulting in a loss of production. A repair by knotting the burst ends together is time-consuming and labor intensive work and in general needs to be performed manually.